Mine fuze

ABSTRACT

1. A pressure activated mine fuze comprising: A. A MINE CASING AND A PRESSURE PLATE ATTACHED TO SAID MINE CASING, SAID PRESSURE PLATE FREE TO MOVE RELATIVE TO SAID MINE CASING WHEN A FORCE IS APPLIED TO SAID PRESSURE PLATE, B. AN ELECTRICAL SIGNAL GENERATOR ATTACHED TO SAID PRESSURE PLATE, SAID ELECTRICAL SIGNAL GENERATOR HAVING A LEVER EXTENDING THEREFROM, SAID ELECTRICAL SIGNAL GENERATOR GENERATING AN ELECTRICAL SIGNAL WHEN SAID LEVER IS MOVED RELATIVE TO SAID ELECTRICAL SIGNAL GENERATOR, SAID LEVER BEING CAUSED TO MOVE BY THE RELATIVE MOVEMENT OF SAID PRESSURE PLATE RELATIVE TO SAID MINE CASING, C. MEANS TO ADJUST THE DISTANCE TRAVELED BY SAID PRESSURE PLATE RELATIVE TO SAID MINE CASING TO CAUSE MOVEMENT OF SAID LEVER, SAID MEANS TO ADJUST OPERABLE FROM OUTSIDE SAID MINE CASING, D. AN INERTIA SWITCH CONNECTED BETWEEN SAID ELECTRICAL SIGNAL GENERATOR AND SAID DETONATOR MEANS, SAID INERTIAL SWITCH ALLOWING SAID ELECTRICAL SIGNAL TO REACH SAID DETONATOR WHEN THE ACCELERATION OF SAID PRESSURE PLATE IS BELOW A PREDETERMINED AMOUNT, AND SAID INERTIA SWITCH MEANS PREVENTING SAID ELECTRICAL SIGNAL FROM REACHING SAID DETONATOR WHEN THE ACCELERATION OF SAID PRESSURE PLATE EXCEEDS SAID PREDETERMINED AMOUNT.

United States Patent 1 Morrow Feb. 20, 1973 MINE FUZE [75 1 Inventor: Warren P. Morrow, Wheaton, Md.

[73] Assignee: The United States of America as represented by the Secretary of the Army [22] Filed: Dec. 3, 1962 [21] Appl. No.: 243,193

[52] US. Cl ..102/19.2, 102/70.2 R, 102/8 ['51] Int. Cl. "F4211 23/26, F42b 21/34 [58] Field of Search.102/l9.2, 70.2, 8, 7, 18, 70.2 G, 102/70.2 GA, 16

[56] References Cited UNITED STATES PATENTS 2,827,850 3/1958 Muzzey ..102/16 2,881,276 4/1959 Mintz et al. ...l02/70.2 2,920,562 111960 Toomey et al ..102/18 2,988,991 6/1961 Elmer ..102/16 3,094,929 6/1963 McGinley et al. 102/192 EXEMPLARY CLAIM 1. A pressure activated mine fuze comprising:

a. a mine casing and a pressure plate attached to said mine casing, said pressure plate free to move relative to said mine casing when a force is applied to said pressure plate,

b. an electrical signal generator attached to said pressure plate, said electrical signal generator having a lever extending therefrom, said electrical signal generator generating an electrical signal when said lever is moved relative to said electrical signal generator, said lever being caused to move by the relative movement of said pressure plate relative to said mine casing,

c. means to adjust the distance raveled by said pressure plate relative to said mine casing to cause movement of said lever, said means to adjust operable from outside said mine casing,

d. an inertia switch connected between said electrical signal generator and said detonator means, said inertial switch allowing said electrical signal to reach said detonator when the acceleration of said pressure plate is below a predetermined amount, and said inertia switch means preventing said electrical signal from reaching said detonator when the acceleration of said pressure plate exceeds said predetermined amount.

2 Claims, 3 Drawing Figures PATENTEI] FEB20 I373 SHEET 2 OF 2 MINE FUZE The invention described herein may be manufactured and used by or for The Government of the United States of America for governmental purposes without the payment to me of any royalty thereon.

The present invention relates to mine fuzes, and more particularly to a pressure actuated mine fuze.

One object of the present invention is to provide a novel pressure actuated mine fuze that will respond only to a predetermined weight or pressure built up on a mine over a considerable, and substantially predetermined, time. That is, a heavy pressure applied in short time will not explode the mine, whereas the same pressure built up over a sufficiently long time will cause detonation. With such a fuze the mine will not be exploded by the shock wave of enemy shells or bombs or by shock waves resulting from the explosion of mine clearing expedients wherein the explosive force of the expedient is used to explode the mine.

Another object of the present invention is to provide a novel pressure actuated mine fuze wherein the amount of pressure needed to actuate the fuze is easily adjustable so that personnel planting the mine field can readily adjust for the soil conditions encountered.

A still further object of the present invention is to provide a novel pressure actuated mine fuze that is relatively immune to blast pressures, and yet compact enough to be used with the World War II U. S. Army M and M 6A2 land mines.

The specific nature of the invention, as well as other objects and advantages thereof, will clearly appear from the following description and from the accompanying drawings, in which:

FIG. 1 is a schematic representation showing the principle components of the fuze of this invention.

FIG. 2 is a vertical partial section showing a specific embodiment of the fuze with an M 15 mine.

FIG. 3 is a detail of an embodiment of a pressure adjusting lever.

The operation of the novel fuze of this invention centers around a combination of an inertia switch with an electrical pulse generator. Detonation, as in prior art pressure activated mines, still requires movement of a mine pressure plate. This movement is used to generate an electrical pulse which is applied to a detonator. In accordance with the teaching of this invention, an inertia switch is provided that will react to a high acceleration of a pressure plate, opening the circuit between the pulse generator and a detonator under shock conditions. Under normal stimulation, with a gradual increase in pressure and resultant slow acceleration of the pressure plate, the inertia switch remains closed, allowing firing of the detonator by the pulse generator.

In FIG. 1 there is shown the components of the novel fuze of this invention in a spread apart relation, in order to facilitate explanation. Reference numeral 11 refers to a relatively fixed base, and reference numeral 12 indicates a pressure plate which moves relative to the base 11. Attached to the pressure plate 12 is a pulse generator 13. The pulse generator 13 may be of the magneto type such as is shown in my application Ser. No., 862,725, now US. Pat. No. 3,062,071. Pulse generator 13 has a plunger or armature lever 14 and a small movement of the lever 14 causes a coil to pass rapidly through a magnetic field generating a relatively high voltage pulse on output leads 15 and 16. The lever 14 is spring loaded, and will return to a normal rest position in the absence of an applied force.

Directly beneath the arm 14 is an adjustable striker 17. Adjustable striker I7 is pivotally attached to the base 11. As is more clearly shown in FIG. 3, adjustable striker 17 may be comprised of a series of steps 18, and an arm 19 which can be accessible at the outside of the mine case. The arm 19 is pivoted on the base 11 so that turning the arm 19 rotates the steps 18. In this manner the distance the pressure plate must move in order for the lever 14 to be actuated may be adjusted.

The output circuit of the pulse generator 13 has an inertia switch 21, and a detonator 22 connected in series. An output pulse from the pulse generator 13 will fire the detonator 22 only when the inertia switch 21 is closed.

Inertia switch 21 is comprised ofa sphere 23, resting upon but not attached to a platform 24. The platform 24 is attached to the movable pressure plate 12. On one side of the sphere 23 is a wall 25 which is connected to the pressure plate 12. A small sphere, or ball bearing, 26 is contained within a cylindrical recess in wall 25, and makes contact with spherical mass 23. The small sphere 26 is forced in an outward direction toward the sphere 23 by a conducting spring 27. Lead 15 makes electrical contact with the conducting sphere 23 through small sphere 26 and conducting spring 27. For reasons that will become more apparent later, the center line of the small sphere 26 is slightly above the center line of the large sphere 23 when the fuze is in the rest, ready-to-fire state shown.

The platform 24 upon which the sphere 23 sits is comprised ofa piece of insulation 28 with an electrical contact 29 upon which the sphere 23 rests. The lead 16 is connected to contact 29 and thereby makes contact with the sphere 23.

Inertia switch 21 is also provided with a restoring bar 31 which is attached to base 11 to restore the inertia switch 21 to a closed condition in the event it has been opened by an explosion or other sharp blast.

The operation of the fuze shown in FIG. 1 will now be explained. As is common with many types of pressure operative mines, (such as the M 15 mine), the distance pressure plate 12 moves relative to the mine base 11 is dependent upon the pressure applied to the plate 12. Under normal conditions the pressure plate 12 will be buried beneath the surface of the earth, and in this case the pressure applied to the pressure plate 12 is dependent not only upon the weight, such as a tank track on top of the mine, but also upon the soil conditions. As will be explained shortly, the pressure required to fire detonator 22 is a function of the distance between the lever 14 and the steps 18. The higher the step 18 which is rotated beneath the arm 14, the less pressure required to detonate the mine.

Intended targets for the mine, such as tanks, apply a gradually increasing force to pressure plate 12 causing it to move toward the fixed plate 11. As the pressure plate 12 moves downward the arm 14 comes in contact with one of the steps 18, causing an upward movement of the arm 14. This upward movement of the arm 14 is used to trigger the pulse generator 13 and thus to generate a detonating signal.

With a relatively slow acceleration of the pressure plate 12 the inertia switch 21 will be closed when the detonator pulse is produced by generator 13. This happens because for relatively slow acceleration of the pressure plate 12, and a resulting slow acceleration of the plate 24, the sphere 23 will fall; be accelerated by the gravitational force at the same rate remaining in contact with the contact 29. Electrical continuity is maintained through lead 16, contact 29, sphere 23, spring loaded sphere 26, and the lead 15.

A steep fronted pressure wave, such as that from an explosion, will cause a rapid acceleration of the pressure plate 12 toward the base 11. In this situation, the base 24 and the wall 25 attached to the pressure plate 12 will move downward rapidly toward base 11. Due to the inertia of the sphere 23 it will instantaneously remain stationary, and contact between sphere 23 and contact 29 will be broken. The contact between the sphere 23 and the contact 29 will be broken before the arm 14 has traveled the distance necessary to strike a step 18. Therefore, when a pulse is generated by pulse generator 13 the inertia switch 21 will have been opened preventing firing of the detonator 22. The spring loaded sphere 26 prevents the large sphere 23 from remaking contact with contact 29 after the sphere 23 and contact 29 have initially separated. This happens because when the wall 25 and the spring loaded sphere 26 move downward toward the base 11 the center line of the sphere 26 moves below the center line of the sphere 23. The sphere 23 is then held away from the contact 29 by the force of spring-loaded small sphere 26 applied below the center line of sphere 23. As the plate 21 gradually returns to its no load position, reset lever 31 holds sphere 23 in place as the plate 21 carries wall 25 and small sphere 26 upward past the center line of the sphere 23. In this position the sphere 23 again makes contact with contact 29 and the fuze is reset.

Referring to FIG. 2, there is shown a fuze of this invention in place in a U. S. Army M mine. Like reference numerals have been used to designate the parts which correspond to those shown and described in connection with FIG. 1. The mine body of the M 15 mine is a relatively large circular shaped can 41 which contains a high explosive. A pressure plate 12 fits snugly, but is free to slide, in a recess 43 formed in the mine casing 41. Pressure plate 12 is provided with a threaded sleeve portion 44 which is adapted to receive a mine fuze.

The fuze shown and described in connection with FIG. 1 is assembled in a housing 45 having a threaded portion 46 adapted to be screwed into the sleeve 44 in the pressure plate 12. The housing 45 is closed by a cover plate 47 held in place by a plurality of screws 48. To make the fuze weather tight, gaskets 49 and 51 are provided. Extending through the plate 47 is the pressure adjusting arm 19.

The housing 45 is attached to one end of a flexible bellows 52, and the other end of the bellows 52 is attached to a base plate 11. When the fuze housing 45 is in place in the pressure plate 12 the base plate 11 rests firmly on the casing 41, and forms the relatively fixed base. Between the base 1 1 and the housing 45 there is a heavy spring 53 which tends to force the housing away from the plate 11. Forces applied to the pressure plate 12 compress the spring 53.

A well portion 55 is provided to receive the fuze detonator 22. Detonator 22 marked A is assembled as part of the fuze and is enclosed in a housing 56 depending from the base 11. If desired, a fuze detonator booster may also be placed in the space marked B in the well 55.

The components and operation of the fuze shown in place in the M 15 mine of FIG. 2. are identical to those shown and described in connection with FIG. 1, with like reference numbers to identify major components. A force applied to the pressure plate 12 forces the pressure plate 12 and the housing 45 downward against the force of the spring 53 until lever 14 of pulse generator 13 strikes one of the steps 18 which are pivotally attached to the base 1 1. If the acceleration of the plate 12 has not exceeded a predetermined amount the inertia switch 21 will remain closed and the mine will explode. If the acceleration of the plate exceeds the predetermined amount the inertia switch will open preventing the firing of the mine. Since the operation is the same as that of FIG. 1, additional explanation would be repetitious and unnecessary.

It will be apparent that the embodiments shown are only exemplary and that various modifications can be made in construction and arrangement within the scope of the invention as defined in the appended claims.

I claim as my invention:

1. A pressure activated mine fuze comprising:

a. a mine casing and a pressure plate attached to said mine casing, said pressure plate free to move relative to said mine casing when a force is applied to said pressure plate,

. an electrical signal generator attached to said pressure plate, said electrical signal generator having a lever extending therefrom, said electrical signal generator generating an electrical signal when said lever is moved relative to said electrical signal generator, said lever being caused to move by the relative movement of said pressure plate relative to said mine casing,

c. means to adjust the distance traveled by said pressure plate relative to said mine casing to cause movement of said lever, said means to adjust operable from outside said mine casing,

. an inertia switch connected between said electrical signal generator and said detonator means, said inertial switch allowing said electrical signal to reach said detonator when the acceleration of said pressure plate is below a predetermined amount, and said inertia switch means preventing said electrical signal from reaching said detonator when the acceleration of said pressure plate exceeds said predetermined amount.

. A pressure activated mine fuze comprising:

. a mine casing, and

. a pressure plate attached to said mine casing, said pressure plate free to move relative to said mine casing when a force is applied to said pressure plate,

c. an electrical signal generator, said electrical signal generator generating an electrical signal when said pressure plate has moved a predetermined distance relative to said mine casing,

f. said inertia switch being connected in series between said electrical generator means and said detonator means, so that electrical continuity is made from said electrical generator to said detonator when said sphere is in contact with said first and second contacts and so that electrical continuity is broken from said electrical generator to said detonator when said sphere is not in contact with said first electrical contact. 

1. A pressure activated mine fuze comprising: a. a mine casing and a pressure plate attached to said mine casing, said pressure plate free to move relative to said mine casing when a force is applied to said pressure plate, b. an electrical signal generator attached to said pressure plate, said electrical signal generator having a lever extending therefrom, said electrical signal generator generating an electrical signal when said lever is moved relative to said electrical signal generator, said lever being caused to move by the relative movement of said pressure plate relative to said mine casing, c. means to adjust the distance traveled by said pressure plate relative to said mine casing to cause movement of said lever, said means to adjust operable from outside said mine casing, d. an inertia switch connected between said electrical signal generator and said detonator means, said inertial switch allowing said electrical signal to reach said detonator when the acceleration of said pressure plate is below a predetermined amount, and said inertia switch means preventing said electrical signal from reaching said detonator when the acceleration of said pressure plate exceeds said predetermined amount.
 1. A pressure activated mine fuze comprising: a. a mine casing and a pressure plate attached to said mine casing, said pressure plate free to move relative to said mine casing when a force is applied to said pressure plate, b. an electrical signal generator attached to said pressure plate, said electrical signal generator having a lever extending therefrom, said electrical signal generator generating an electrical signal when said lever is moved relative to said electrical signal generator, said lever being caused to move by the relative movement of said pressure plate relative to said mine casing, c. means to adjust the distance traveled by said pressure plate relative to said mine casing to cause movement of said lever, said means to adjust operable from outside said mine casing, d. an inertia switch connected between said electrical signal generator and said detonator means, said inertial switch allowing said electrical signal to reach said detonator when the acceleration of said pressure plate is below a predetermined amount, and said inertia switch means preventing said electrical signal from reaching said detonator when the acceleration of said pressure plate exceeds said predetermined amount. 